Bandwidth Utilization: Multiplexing and Spreading Chapter 6 Bandwidth Utilization: Multiplexing and Spreading Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Topics discussed in this section: 6-1 SPREAD SPECTRUM In spread spectrum (SS), we combine signals from different sources to fit into a larger bandwidth, but our goals are to prevent eavesdropping and jamming. To achieve these goals, spread spectrum techniques add redundancy. Topics discussed in this section: Frequency Hopping Spread Spectrum (FHSS) Direct Sequence Spread Spectrum (DSSS)

Spread Spectrum A signal that occupies a bandwidth of B, is spread out to occupy a bandwidth of Bss All signals are spread to occupy the same bandwidth Bss Signals are spread with different codes so that they can be separated at the receivers. Signals can be spread in the frequency domain or in the time domain.

Figure 6.27 Spread spectrum

Figure 6.28 Frequency hopping spread spectrum (FHSS)

Figure 6.29 Frequency selection in FHSS

Figure 6.30 FHSS cycles

Figure 6.31 Bandwidth sharing

Figure 6.32 DSSS

Figure 6.33 DSSS example